Continuous washing paths established by a washing drum and through which the items are laundered are passed substantially continuously by rotational transfer through drum rotation or by operation of a screw are of course known. The rotary drum type machines are evident from the references contained in the above-identified application and the construction of machines using worms will be apparent from the commonly owned U.S. Pat. Nos. 4,422,309 and 4,494,265 and the documents of record in the files thereof.
Generally these items are passed through the washing machine in a direction opposite to the flow of washing or running liquid and especially in the washing process to conserve water and energy.
A single counterflow cycle washing machine drum often may be divided into an initial soaking zone having two or more compartments, an outer washing zone which can have a comparatively large number of compartments and a rinsing zone which can have fewer compartments than the washing zone.
The items to be washed are fed to a loading chamber and thereafter are transferred in discrete batches from one chamber to another through the individual zones according to a cyclic process.
In the system described in the aforementioned applications, the drum may angularly oscillate about its axis to a certain extent to agitate each batch in the respective chamber in a corresponding treatment liquid and in accordance with the desired washing cycle. Then a further rotation of the drum can automatically transfer the batches in a direction of movement into the next compartment.
Toward the end of the wash drum or trommel which is relatively downstream in the direction of movement of the wash, fresh water can be supplied to at least partially flow through the washing trommel in counterflow to the laundered articles. These processes are problem-free as long as only white articles of laundry are washed in the apparatus.
In recent years the proportion of colored articles, for example, green or blue laundry, colored bedding, table clothes or napkins, is relatively large and is expected to grow.
However, when brightly colored and white articles are laundered together in a conventional cyclic washing unit, problems are encountered because colored particles can be entrained from colored fabrics to the white fabrics and can discolor them.
To avoid such discoloration of the white wash, colored material has either been washed in a separate machine or in a bath-change washing stretch which does not work in counterflow, thereby eliminating the possibility of entrainment of such particles onto upstream white wash from comparatively downstream colored laundry.
This means higher invention costs since a bath-change washing stretch is considerably more expensive than a counterflow washing machine and this means higher washing costs. The operational costs are likewise higher. One can avoid or limit transfer of coloring from pigmented articles to white wash in a counterflow washing machine by leaving the bulk of the washing chambers empty. In practice this has meant that 60 to 70% of the washing chambers or compartments will remain empty when strongly colored materials are washed. Naturally this reduces the performance of the machine considerably because water, steam and washing liquors must be supplied in the same amounts even when there is no wash in some of the chambers.
In order to eliminate these empty chambers and the difficulties involved in their use, the liquid counterflow can be bypassed around the wash chamber in which a colored batch of laundry may be present. This maintains counterflow elsewhere but eliminates the counterflow for chambers containing problematical wash. An expensive and cumbersome control apparatus is required for this system.